Genome editing technologies including CRISPR/Cas9 have enabled us to knock‐out gene(s) in mammalian cells with high efficiency and low cost.24 It has been reported that NANOG‐deficient prostate cancer cells generated by the CRISPR/Cas9 system showed a significant decrease in tumorigenicity, compared with parental cells.27 Thus, we decided to employ this technology to study the pathological roles of CD44s in liver CSCs. This evidence concerns the gene NANOG and prostate cancer.